Not Applicable.
1. Field of the Invention
The present invention relates generally to pivot bearing cartridges for use in head stack assemblies, and more particularly to a pivot bearing cartridge including a ball bearing set and a magnet element for ball bearing set pre-loading.
2. Description of the Prior Art
The typical hard disk drive includes a disk drive base, and a head disk assembly (HDA) and a printed circuit board assembly (PCBA) attached to the disk drive base. The head disk assembly includes at least one magnetic disk, a spindle motor for rotating the disk, and a head stack assembly (HSA) that includes at least one transducer head, typically several, for reading and writing data from the disk. The printed circuit board assembly includes a servo control system in the form of a disk controller for generating servo control signals. The head stack assembly is controllably positioned in response to the generated servo control signals from the disk controller. In so doing, the attached heads are moved relative to tracks disposed upon the disk.
The head stack assembly includes an actuator assembly, at least one head gimbal assembly, and a flex circuit cable assembly. A conventional xe2x80x9crotaryxe2x80x9d or xe2x80x9cswing-typexe2x80x9d actuator assembly typically comprises an actuator body that rotates on a pivot assembly between limited positions, a coil portion that extends from one side of the actuator body to interact with one or more permanent magnets to form a voice coil motor, and one or more actuator arms that extend from an opposite side of the actuator body. A head gimbal assembly includes at least one transducer head, sometimes two, which is distally attached to each of the actuator arms. The actuator assembly includes the actuator body which has a bore and a pivot bearing cartridge engaged within the bore. The at least one head gimbal assembly and the flex circuit cable assembly are attached to the actuator assembly.
The pivot bearing cartridge typically includes a pivot shaft having a threaded end, a pivot sleeve, and vertically separated upper and lower ball bearing sets mounted upon the pivot shaft which facilitate rotational attachment of the pivot sleeve to the pivot shaft. The pivot sleeve is disposed within the bore of the actuator body for allowing the pivoting of the actuator assembly. The threaded end of the pivot shaft used to mount the pivot bearing cartridge, and therefore the actuator assembly, to the disk drive base. Each ball bearing set includes inner and outer ball bearing races which encase a plurality of ball bearings. The inner ball bearing races engage the pivot shaft and the outer ball bearing races engage the pivot sleeve. This configuration allows for rotational movement of the outer ball bearing races relative to the inner ball bearing races for rotation of the pivot sleeve. The upper and lower ball bearing sets are pre-loaded in compression to maintain the pivot sleeve in position with respect to the pivot shaft.
A topic of concern is the desire to reduce the overall disk drive size. Such disk drives may have a variety of applications such as in hand held or portable electronic devices. The exterior size and shape of the disk drive is often referred to as a xe2x80x9cform factorxe2x80x9d. Reduction of such disk drive form factor has proven challenging. This is because the mere reduction of the size of the various disk drive components may result in such components being unable to conform to required specifications and standard form factors for such components, and may result in installation or assembly difficulties. As such reduced sized disk drives may have applications in hand held or mobile electronic devices, the specifications may even be tighter as compared to personal computer applications. For example, those specifications related to susceptibility to damage resulting from shock.
One particular area of focus is the reduction of the height of the pivot bearing cartridge as this limits the overall sizing of the head stack assembly. In a typical configuration, the pivot bearing cartridge height may be a function of the upper and lower ball bearing set arrangement. The mere reduction of the sizing of the upper and lower ball bearing sets impacts the susceptibility to damage resulting from shock, potential use of non-standard form factor bearings and difficulties conforming to allotted space requirements for such bearings. Accordingly, there is a need in the art for an improved pivot bearing cartridge configuration in comparison to the prior art.
An aspect of the invention can be regarded as a pivot bearing cartridge for use in a head stack assembly. The pivot bearing cartridge includes a pivot shaft including a central axis, a shaft body and a shaft distal end. The pivot bearing cartridge further includes a pivot sleeve disposed about the pivot shaft. The pivot sleeve includes a pivot sleeve annular body and a pivot sleeve closed end disposed adjacent the shaft distal end. The pivot bearing cartridge further includes a ball bearing set disposed between and in mechanical communication with the shaft body and the pivot sleeve annular body. The pivot bearing cartridge further includes a shaft magnet element attached to the shaft distal end adjacent the pivot sleeve closed end. The shaft magnet element is sized and configured to apply a magnetic force to the pivot sleeve in a direction along the central axis for pre-loading the ball bearing set.
According to various embodiments, the shaft magnet element may be sized and configured to apply an attractive magnetic force to the pivot sleeve in a direction along the central axis for pre-loading the ball bearing set. The shaft magnet element may be disposed within the shaft body. The shaft magnet element may include an exposed surface facing the pivot sleeve closed end. The pivot sleeve may include a pivot sleeve insert disposed at the pivot sleeve closed end adjacent the shaft magnet element for magnetically interacting with the shaft magnet element. The pivot sleeve insert may be formed of a magnetic metal material, such as a steel. In another arrangement, the pivot sleeve insert may be formed of a magnetic material. The shaft body may extend to a shaft distal annular surface concentrically about the shaft magnet element facing the pivot sleeve insert.
In addition, according to another aspect of the present invention, there is provided a head stack assembly. The head stack assembly includes a rotary actuator including a bore, and a pivot to bearing cartridge as described above. The pivot sleeve is positioned within the bore of the rotary actuator. According to another aspect of the present invention, there is provided a disk drive including a disk drive housing, and a head stack assembly as described above rotatably coupled to the disk drive housing.
According to another aspect of the present invention, there is provided a pivot bearing cartridge for use in a head stack assembly coupled to a disk drive housing. The pivot bearing cartridge includes a pivot shaft including a central axis and a shaft body along the central axis. The pivot bearing cartridge further includes a pivot sleeve including a pivot sleeve annular body and a first pivot sleeve end disposable adjacent the disk drive housing. The pivot bearing cartridge further includes a ball bearing set disposed between and in mechanical communication with the shaft body and the pivot sleeve annular body. The pivot bearing cartridge further includes a pivot sleeve magnet element attached to the first pivot sleeve end. The pivot sleeve magnet element is disposable adjacent the disk drive housing. The pivot sleeve magnet element is sized and configured to apply a magnetic force to the disk drive housing in a direction along the central axis for pre-loading the ball bearing set.
According to various embodiments, the pivot sleeve magnet element may be sized and configured to apply a repulsive magnetic force to the disk drive housing in a direction along the central axis for pre-loading the ball bearing set. The pivot sleeve magnet element may be annular shaped. The pivot shaft may include a shaft base. The shaft base extends radially from the central axis with the shaft body extending from the shaft base along the central axis. The shaft base is attachable to the disk drive housing, and the first pivot sleeve end is disposed adjacent the shaft base. The pivot sleeve magnet element is disposed adjacent the shaft base, and the pivot sleeve magnet element is sized and configured to apply a magnetic force to the shaft base in a direction along the central axis for pre-loading the ball bearing set. The shaft body may be integrally formed with the shaft base. In addition, the shaft base may be integrally formed with the disk drive housing. The shaft base may include a base magnet element. The pivot sleeve magnet element is disposable adjacent the base magnet element, and the pivot sleeve magnet element and the base magnet element are sized and configured to apply magnetic forces with respect to each other in a direction along the central axis for pre-loading the ball bearing set. The base magnet element may have a diameter the same as a diameter of the pivot sleeve magnet element. Alternatively, the base magnet element may have a diameter greater than a diameter of the pivot sleeve magnet element. The base magnet element may be annular shaped.
In addition, according to another aspect of the present invention, there is provided a head stack assembly. The head stack assembly includes a rotary actuator including a bore, and a pivot bearing cartridge as described above disposed within the bore. According to another aspect of the present invention, there is provided a disk drive including a disk drive housing, and a head stack assembly as described above rotatably coupled to the disk drive housing.